Well blowout preventer control pressure modulator

ABSTRACT

The constriction of a packer or other tool about a pipe string being run in a well is altered in such manner while a pipe joint is passing through the packer as to facilitate rapid running of the string in a well and to reduce wear of the packer.

United States Patent [is] 3,695,349 Murman et a1.- [45] Oct. 3, 1972[54] WELL BLOWOUT PREVENTER 3,103,976 9/1963 DeVries ..166/.6 CONTROLPRESSURE MODULATOR 1,894,912 1/ 1933 Otis 166/77 X Inventors: n o man aos ve des I Minor a 2,188,141 1/1940 Abercrombie ..25l/1 X Peninsula,George E. Lewls, Arcadkr Charles E 01mm Whittier 2,721,614 10/1955Simmons ..166/77 X a ofcanf 3,207,221 9/ 1965' Cochran et a1. ..l66/88 X1 3,215,203 11/1965 Sizer ..l66/77 [73] Assignee: Hydril Company, LosAngeles,

Calif. Primary Examiner-Marvin A. Champion Assistant Examiner-Richard E.Favreau [22] filed March 1970 Attorney-White, Haefliger and Bachand [21]Appl. No.: 21,130

[57] ABSTRACT [52] US. Cl. ..166/.5, 251/1, 166/84 The constriction of apacker or other tool about a pipe [51] Int. Cl. ..E2lb 33/035 stringbeing run in a well is altered in such manner [58] Field of Search....166/53, 84, 86, 75, 82; 251/1; while a pipe joint is passing throughthe packer as to 277/28, 34, 103, 73 facilitate rapid running of thestring in a well and to reduce wear of the packer. [56] References CitedUNITED STATES PATENTS v 37 Claims, l2 Drawing Figures 3,533,468 10/1970Lewis etal ..'.....251/1 X PATENTED T 3 SHEET 3 [IF 4 OPENlNG CHAMBER TOFourz- WAY com-Q01. VALVE fxvvewrales.

END/V00 MueAm/v 050/1265 E. LEW/.5 (IE memes E. OB/Q/E/V ELL arowourPREVEN'IER comm. rnnssrm: MODULATOR BACKGROUND OF THE INVENTION Thisinvention relates generally to the control totool engagement withvertically movable well strings, and more particularly concerns thereduction of resistance to vertical travel of such stringsthroughpackers closed about such strings. r I

' lnwell drilling operations it is frequently the'practice to 'constricta packer element, (as for example in a flow-out preventer) about thedrill string so as to shutin the gas pressure in the wall annulus. Suchconstric- Preventer (Model GKI 5000) at only a few inches per second,whereas. the string'between successive joints may be traveled.at"several feetpersecond through the constricted packer. v

The above problem becomes extremely critical in off-shore, sub-seapacker installations where a drill string is suspended from a drillingbarge. It is found that SUMMARY OF THE INVENTION Itis a major object ofthe invention to provide ap-' paratus ,and method for overcoming theabove described problems. Basically, the method of the invention isapplicableto a-system that includes packer means, typically-annular,that is laterally constricted to engage a well string being passedlongitudinally I typical joint through the packer of a-Hydril Blow-outthe constricted packer without substantially increased resistance tosuch passage, and without requiring reduction of speed of travel of thestring, and also without materially increasing the rate of wear of thepacker material.

In its apparatus aspects the invention comprises, in such a system asdescribed, supply means to selectively supply actuating fluid pressureto the chambers; and modulator means in communication with the fluidpressure supply to the first chamber and operably to relieve such excesspressure development. Typically, the

modulator means is in operative communication with the second chamber toeffect sudden fluid pressure increase in the latter in response tosudden excess pressure development in the first chamber. As will beseen, the modulator means may include a by-pass valve controlling fluidpressure communication to the second chamber, together with biasingmeans (as for example the pressure of control fluid stored in anaccumulator) yieldably biasing the by-pass valve toward a positionblocking communication of actuating fluid pressure from the first to thesecond chambers.

Additional objects include the provision of a control valve (as forexample a four-way valve) for controlling supply fluid pressurealternately to the first and second chambers as described, that valvehaving a position in through thepacker, and means including a packeractuator forming a first chamber receiving fluid pressure acting to urgethe actuator in a direction to effect such packer construction, and, asecond chamber subsequently to receive fluid pressure acting to urge theactuator in a direction relieving packer constriction to allow expansionof the packer away from the string, the pressure in thefirst chamberbeing subjected to in crease to excessive level in response toengagement of an enlargement (such as a joint) in the string with theconstricted packer and tending to expand same. The method steps includecontinuing the supply of actuating fluid pressure to the first chamber;and suddenly increasing the fluid pressure in the second chamber inresponse to the enlargement engagement with the packer. Typically, thesudden increase is effected by which it communicates the second chamberwith an outlet via piping of such length that an actuating pressure wavepassed by the by-pass valve is supplied to the second chamber prior totransmission to the outlet via the control valve; the location of theby-pass valve either outside or inside a housing for the packer; theprovision of a signaling circuit comprising a switch operable inresponse to by-passing of fluid to the second chamber via the modulatormeans and a signaling device (as for example on a drilling barge)electrically connected in circuit with the switch. Accordingly, theoperator may elevate or lower the pipe so that the switch is notoperated in response to vertical stroking of the string due to waveaction on the barge, whereby he is assured that pipe joints are notpassing up and down through the constricted packer, reducing wearthereof. Finally, the invention is applicable to use with stringengaging tools other than radially constrictable packers, i.e., forexample pipe rams.

These and other objects and advantages of the invention, as well as thedetails of an illustrative embodiment, will be more fully understoodfrom the following description and drawings, in which:

DRAWING DESCRIPTION FIG. 1 is an elevation showing a sub-sea well headassembly;

FIG. 2 is a vertical elevation, taken in section, show ing a preventerassembly in closed or actuated condition;

FIG. 3 is a view showing a control system for the preventer, or similarpreventers;

FIG. 4 is an elevation taken in section through a control valve in theFIG. 3 system;

FIG. 5 is a view showing a manually operable system for the preventer;

A FIG. 6 is a fragmentary elevation showing a modifi- FIGS. -12 aresections showing modified control valves.

DETAILED DESCRIPTION Referring first to FIG. 1, the blow-out preventerassembly 10 is shown connected in a sub-sea stack 100 also including aseries of ram-type preventers 101. A riser system 102 extends above thestack and is connected thereto by a well head connector 103. Riser pipeextends to the sea surface, and typically to a drilling barge 104 orother installation, and it is clear that wave action will cause thebarge to move up and down, displacing suspended pipe up and down in theriser and the blow-out preventers.

. Turning to FIG. 2, the control head or preventer assembly, generallyindicated at 10, includes a body member 11, having concentric bores l2,l3 and 14, which are of progressively increased diameters. Cap 16 isreleasably held to the body member by screw thread connection 17 in sucha position that the face 19 of cap flange 20 engages the upper end 21 ofthe body member 11, and cap and body member being packed off at 22. Cap16 has a bore 23 which is of the same diameter and is concentric withbody bore 12. Sunk in the upper face of cap 16 are bolt holes 24 for theattachment of equipment thereabove. The annular groove 25, in that upperface, is adapted to receive a sealing ring for sealing engagement withsaid equipment.

The neck 26 of body member 11 has an attachment flange 27 wherebyconnection is made through bolts 28 to the flange 29 or any othersuitable fitting.

Cap 16 has an internal annular flange 35 which defines the downwardcontinuation of bore 23, and a peripheral flange 36 which defines bore37, said bore 37 being concentric with all the body-member boresidentified above.

The body 11 has an annular, upstanding flange 38 which engages thepacker actuating member 39 at 40 to limit the extent of downwardmovement of said member. The actuator 39 has a piston portion 41, havingpiston-fit in bore 14, and piston portion 42 which has piston-fit inbore 13. The actuator is extended upwardly at 43, extension 43 havingpiston-fit in the capflange bore 37. Sealing rings 44, 45 and 46 areprovided between piston portions 42, 41 and 43, respectively, and therespective cylinder defining walls which receive those portions.

Piston 41 divides body bore '14 into upper and lower cylinders orpressure chambers 47 and 48, ports 49 and 50 opening, respectively, fromthose chambers. External pipes 51 and 52 open to ports 49 and 50,respectively. Note that the outer diameters (14) of chambers 47 and 48are equal, and the inner diameters (l3) and 37 of these chambers may beequal, for balancing purposes. I

The actuator 39 has a downwardly and inwardly tapering conical bore 53,and the actuator portion 43 which defines this bore may be consideredbroadly as an internal, conical wedge, or as a packer-constrictingelement.

Packer P includes a massive annulus or sleeve 55 of an elastomer and,preferably, resilient material such as rubber or Neoprene. In mostinstances, it is intended that a single packer be adapted for repeatedopening and closing operations, and therefore it is preferable that ithave relatively high resilient characteristics, so it may beself-restoring to open position when the constricting force is removed.From this point on in the description, it will be assumed that thepacker has such resilient characteristics, but this assumption is notconsidered as limitative on my broader claims. It has been found thatrubber having a durometer hardness of about 75 is suitable for generaluse in my packer but, again, this specification of relative hardness isnot to be considered as limitative. The packer is shown as an unsplit,continuous annulus, but it will be understood that the disclosure is notlimited to a packer wherein there is no split, so long as there is noangularly extending gap interrupting the continuity of the packer attimes when it is inwardly contracted into sealing engagement withmembers positioned within its bore.

Included in the make-up of the packer is a series of rigid,rubber-flow-control elements 56. These elements may take different formsand still lie within the scope of my broader claims, but I will firstdescribe the preferred form of elements which has individual features ofadvantage. These rigid control elements are individually movable bodilywith the rubber in its movement of radial contraction and expantion andalso, to a limited extent, movable individually with respect to therubber as will later appear. Taken together, the rigid control elementsmay be considered as a radially expansible and contractible armatureembedded and bonded within annulus 55.

Molded annulus 55 has an outer conical face 57 which is complementary toactuator bore 53, and a bore 58 which has a central, substantiallycylindrical portion 59 and oppositely inclining upper and lower portions60 and 61, respectively; the outward flare, in each case being towardthe associated end of the annulus.

It will be seen that each element 56 comprises top and bottom plates 63and 64, respectively, rigidly connected by vertical rib 65, the outerfaces 66 of the plates and the outer face 67 of the rib havingsubstantially the same degree of taper as bore 53 and annulus face 57.Or plates 63, 64 may be considered as transverse flanges on rib 65.Elements 56, which may be of steel, bronze, or any other suitable rigidmaterial, are preferably positioned in the rubber at the time of moldingand, preferably, the rubber and the elements are bonded together by theuse of suitable adhesive during the molding process. The plates of thecontrol elements are sectorial in shape, as viewed in plan, and arearranged in a circular series, with spaces left between the opposingside edges of the plates, both top and bottom. The plates are so sizedthat the two opposed sides edges of adjacent elements are spaced apart,it following that as the elements move radially inward, the spacesbetween these, will diminish to fonn a line contact from end to end ofthe plates. This will prevent the rubber which will flow during theconstriction of the annulus from being pinched off at the radiallyinward ends of the plates.

The annulus 55 is molded so its outer annular portion 72 projectsradially outward beyond the outer faces 66 of the plates, it followingthat these metallic faces do not engage the wall of actuator bore 53.For purposes of later description, annular portion 72 is considered asbeing that portion which extends radially from face 57 to the outerfaces 67 of ribs 65.

The packer is lowered; while cap 16 is detached; into the position ofFIG. 2, the actuator 39 then being in the fully down positiomand theannulus 55 nicely fitting the upper portion of bore 53 without requiringappreciable radialconstriction of the annulus. For positively limitingthe downward movement of the annulus, a stop is provided in the form oftube 74 which is retained in housing bore .15. The upper end of thetubeprovides the, packer stop. The bore 75 of this tube is of the samediameteras bores 12 and 23,-and the tube is annularly spaced from bothpiston portion 42-and the lower end of actuator wedge-portion 43.-Ports76 open from bore 75 to chamber 77, while latter is annularly defined bythe tube and the sleeve 80, there being a seal at 78.

When cap '16 is subsequently secured in .place, its horizontalunder-surface 79 providesa stop for limiting upward movement of thepacker, the upper plates 63 of control elements 56 sliding over thissurface" as the packer is radially constricted or expanded. Tube end andcap surface-79thus form vertically spaced stops which preventappreciable vertical movement of the packer with relationto the bodymember 11.

.It will be seen that the radial constriction of the packer isaccomplished by virtue of relative vertical movement between thepackerand the actuator. While the illustrated embodiments show thisrelative movement as brought about by holding the packer againstvertical movement with respect to the body member and then moving theactuator vertically with respect to the housing and packer, it will beunderstood the arrangement and operation may be reversed.

The sleeve 80 may be considered as part of the housing structure 11, towhich it is retained by the faster 81. The sleeve 80 and body 11,together with actuator piston portion 42 from a" third chamber 82 toreceive control pressure fluid (as via porting 83 and pipe 84) acting tourge the actuator upwardly in at least partly counterbalancing relationto downward force exertion on the actuator. In particular, such downwardforce to bl so counteracted maytypically result from the static pressurep of a column of drilling mud in the annulus 85 outside the drill pipe86, such mud circulating downwardly in that pipe to the bit, and risingin the annulus.

FIG. 1 shows the riser 87 within which the mud flows to the surface. Themud pressure is applied to the packer P tending to expand it, anddownward thrust is thereby transferred to the actuator 39 across,enlarged tapered surfaces 57 and 53, when the packer is closing in thewell. See in this regard co-pending application Ser. No. 785,891,entitled, Well Pressure Compensated Well Blowout Preventer wherein thesupply of counterbalancing fluid pressure to chamber 82 via pipe 84 isdiscussed.

Extending the description to FIG. 3, a gas pressure vessel 90 is shownas communicating with pipes 51 and 52 via a suitable pressure regulator91 and four-way valve 92. In one position of the latter, as illustrated,pressure fluid is delivered to pipe 52 for closing the preventer packer,and pressure fluid in pipe 51 is exhausted at 93 to the sea or returnedto the surface. In

the alternate position of the valve 92, pressurevfluid is delivered topipe 51 for opening the preventer packer, and fluid in pipe 52 isexhausted to the seaor returned to the surface. As explained in theco-pending application referred to above, counterbalancing fluidpressure may also be supplied to chamber 82 via pipe 84. Controls forthe regulator 91 and valve 92 are indicated at 94 and 95, and may beelectrically operated from the surface.

Coming now to that portion of the description highlighting theinvention, it will be noted hat the string 86 may typically haveconnectors or collars interconnecting the string pipelengths 111, theconnectors being of larger diameter than such pipe. It is often desiredto maintain the packer closed about the pipe while the latter is runlongitudinally into or out of the well or while the pipe moves up anddown due to wave action onthe barge, as referred to; and it isfound thatrapid vertical displacement of the connectors through the closed packertends to excessively wear the packer rubber necessitating itsreplacement at great expense. In this-regard, with several hundredpounds of closing fluid pressure applied to chamber 48, excessivepressure builds up in the latter as the connector 110 engages the closedpacker and attempts to expand it and thereby urge the actuator 39downwardly.

In accordance with the invention, modulator means is provided in thisenvironment, and in communication with the pressure supply to closing(i.e. first) chamber 48, for relieving the excess pressure developmentin that chamber, that developed pressure at times being greater than1,500 p.s.i. As will be seen, the relief is such as to enable theenlarged connector to pass without difficulty through the packer, i.e.,without excessively wearing the packer while at the same time the packerremains in closed and annular sealingengagement with the connector andpipe string vertical speed not being reduced during such passage.Typically, a bypass passage or pipe may be provided as at 1 13communicating between the chambers 47 and 48, as for example via pipes51 and 52, and the modulator means may comprise a check valve unit as at114 controlling the by-passing of excess fluid pressure from closingchamber 48 to opening chamber 47.

FIG. 4 shows one form of modulating check valve unit which alsoaccommodates biasing to control the pressure level at which suchby-passing occurs. lt comprises a body 115 having a threaded inlet 116for bypass pipe branch 117 connected to pipe 52, and a threaded outlet118 to receive the terminal of by-pass pipe 113. Received within thebody bore 119 is a seat ring 120 against which a valving stopper such asa ball 121 is urged by a plunger stem 122. The plunger or piston body123 is urged by spring 124 toward the ball, theopposite end of thespring being seated by a plug 125 having threaded reception at 126 inthe body 1 15. In this regard, the effective area of the piston 123 maybe equal to or greater than the effective area of the opening 120adefined by the ball seat, so that the ball will be held closed againstthe seat prior to pressure increase in line 117 created by attemptedpassage of a connector through the closed packer.

Plunger 122 is also urged toward the ball 121 by control fluid pressurein chamber 127, and supplied from an accumulator 128 via piping 129. Theaccumulator receives fluid under pressure from the line 130 connectingthe discharge side of the regulator 91 with the control valve 92, therebeing a check valve 131 in line 130 downstream of the location 132 atwhich the accumulator communicates with line 130 via branch 133. As aresult, the control fluid pressure supplied by bypass valve chamber 127remains at a level in part determined by the regulator 91, the excesspressure developing in the preventer closing chamber 48 being blocked bycheck valve 131 from communication to the accumulator. Check valve 131is not needed if lines 129 and 250 or 250a are sufficiently long, as forexample where they extend from the surface.

When that excess pressure reaches a level determined by the regulatedlevel and the tension of spring 124, the by-pass valve stopper or ball121 opens and the excess pressure is immediately communicated to theopening chamber 47. Relief of pressure'build-up in closing chamber 48may typically occur within less than a second following its suddenbuild-up. Also, the extent of relief may be such that the connectorfreely passes through the packer, with clearance permitting slight fluidleakage th'erebetween, the advantages being minimum wear of the packerand rapid passage of the connector therethrough. In FIG. 3 control valveconfiguration, chamber 47 remains in communication via elongated pipe134 with the discharge or outlet point 135, so that the excess pressuremay bleed at a slower rate to the discharge, due to the restriction toflow imposed by the pipe 134.-ln other words, when valve stopper 121opens, the excess pressure wave is first communicated to chamber 47, andlater to the discharge, causing a downward force on the piston 39 toopen the packer P to allow free passage of tool joint 110 through thepacker. Note that the pressure in the opening chamber 47 and in valvebody bore 119 typically will not be less than that of the sea water atthe sub-sea level of the equipment, during the time valve 92 is in theposition shown in FIG. 3. Accordingly, the pressure delivered by theregulator 91 to close the packer about the string 86 must besubstantially greater than the sub-sea pressure at the equipment level.Regulator 91 may be conventional, and include a valve controllingdiaphragm exposed to pressure in line 91a and to spring tension adjustedby control 94. Finally, accumulator 128 may be made integral with themodulator valve unit 114. Check valve 131 may be eliminated if 5 line250 between the accumulator and the by-pass valve is of length such thatthe excess pressure wave is by-passed at 114 prior to return via line250 to the aceumulator.

I FIG 10 illustrates the provision of an adjustable insert 230 threadedat 231 into plug a corresponding to plug 125 in FIG. 4. Rotation of theinsert adjusts the tension in spring 124a, for control of by-passingpressure.

A further feature of the invention concerns the provision of a signalingcircuit comprising a switch or other means indicated at in FIG. 3operable in response to by-passing of the fluid by valve 114, and asignaling device 141 (see FIG. 1) electrically connected in circuit withthe switch, as via cable 142. The switch may be pressure responsive andin communication with fluid pressure in line 113. Accordingly, thesignaling circuit enables detection by the operator at the surface of anincrease in pressure in the closing chamber 48 to excessive level, asresults from passage of a connector 110 into or through the closedpacker annulus, wave action of the drilling barge for example lifting orloweringthe pipe to effect this condition. He may then adjust the pipestring as by lifting or lowering same so as to obviate the condition, atwhich point the signaling device 141 at the surface is no longeractuated on and off at wave cresting or troughing intervals, wherebywear of the packer is substantially reduced.

FlGQS illustrates a modified system characterized by hand operation, orhand-controlled operation of one or more of the valves 150, and 151. Inone position of four-way valve 151, actuating fluid pressure is appliedto the packer closing chamber, (corresponding to chamber 48) in thepreventer assembly 153; and likewise, in the alternate position of valve151, actuating fluid pressure is applied to the packer opening chamber(corresponding to chamber 47). The above assumes that by-pass valveremains closed. Upon the occurrence of excess pressure in the closingchamber, as communicated by the gauge 155, the operator may momentarilyopen the by-pass valve 150 to bleed the excess pressure developed in theclosing chamber (as by passage of a connector 156 through the closedpacker) to the opening chamber, for the purpose and with the resultsdescribed above.

The by-passing function may alternatively be effected within thepreventer housing as by a valve 160 protectively housed in the wall ofthe housing 11a of the blow-out preventer assembly, in FIG. 6. Controlpressure is led to the valve biasing piston 123a as via a pipe 161, thepiston being retained in an insert 162. Bypass ducts in the wall areseen at 163 and 164 communicating with chambers 48a and 470 at oppositesides of the actuator piston 41a. Ducts 49a and 50a correspond to ducts49 and 50in FIG. 2.

Further, as seen in FlG. 3, the by-passing function may be supplementedby use of a modulating valve similar to valve 114, and connected betweenpipe 84 and pipe 51, to by-pass excessive pressure in chamber 82 to theopening chamber.

Referring to FIG. 7, isolation is there provided between the opening andclosing pressure lines 51a and 52a connected to the housing 11 and inFIG. 2, and the modulated means generally indicated at 199, the latterfunctioning to relieve excess pressure development in the closingchamber of the preventer unit 10. Means 199, which may be supplied as aseparate and complete unit to be operatively combined with thepreventer, includes the modulator or by-pass valve 200 having the samemode of operation as that shown in FIG. 4. Pressure from the closingchamber of the preventer is supplied via line 201 to the inlet side ofthe valve; pressure from the outlet side of the valve is communicated tothe preventer opening chamber via line 202; and control pressure fromline 201 is normally supplied to the piston side of the valve 200 vialine 203, shuttle valve unit 204, and line 205. An accumulator 206 isalso connected with line 205, and line 205 contains an orificerestriction at 198.

If pressure in line 201 increases due to attempted passage of the pipeconnector 207 through the packer within the preventer 10, the by-passvalve opens and the excess pressure is supplied via line 202 to theopening chamber, as previously described. Any excess then flows via thatchamber to line 510 leading to the fourway valve and then to the surfaceor to the sea. lf presclosing chamber because shuttle ball 204a will bedisplaced from seat 209 to seat 208, in chamber 308. Restriction 198prevents sudden loss of accumulator pressure to exhausting line 201 or202, while ball 204a shifts position to block such loss. Note theaccumulator pressure equals that in line 201 or 202 to which it isconnected. t Referring to FIG. 8,"the construction is the same as inFIG. 7, excepting that the shuttle valve is eliminated, and insteadcontrolpressure is supplied to the accumulator 206 and to the pistonside of the by-pass valve 200 from a surface control unit 210, viapiping 211. This adds versatility, and permits the surface operator todetermine when the modulator means is to be operative and inoperative.-For example, he, may supply suflicient control pressure to preventthe'by pass valve from operating should thatbe desired.

FIG. 9 is similarlto FIG. 8, and illustrates a modifiedsystem'characterized by remote control of the biasing pressure appliedto the piston chamber in the valve 200, and from a pressure sourcedifferent from that used to operate the preventer. The by-pass pressurelevel is determined by the adjustment at 213 of pressure regulator 212,and that level could be substantially greater than the pressure suppliedto the preventer via line 217 at times when the by-pass valve is toremain in- I operative. Line 214 connects an accumulator 215 with theregulator, and the line 216 connects the regulator with the controlpiston side of the by-pass valve. Pressure from an accumulator 218 issupplied to line 217 via regulator 219 and four-way valve 220. Whenvalve 220 is in the alternate position, pressure is supplied via line221 to the preventer opening chamber. The provision of two separatedpressure sources 215 and 218 makes unnecessary the check valve seen at131 in FIG. 3, isolation being provided at the pressure source.

Referring back to FIG. 8, a pressure differential switch 320 (or flowswitch) is located in a branch line 321 connected into line 202 atopposite sides of the orifice 222. Electrical wiring 323 connects theswitch with a surface indicator as at 141 in FIG. 1, which signals whenpressure from the closing chamber is by-passed to the opening chamber.The orifice 222 provides an increased differential pressure thereacrossin response to the by-passing of increased pressure to the openingchamber, and sufficient to operate the switch. In FIG. 9, a signalingpressure switch 230 is connected in the discharge line 231 from thefour-way valve 220, and upstream of the restriction means 232 in thatline, the switch being operated when the excess pressure from line 201is by passed at 200 to line 202, then to line 221, the four-way valveand line 231.

FIG. 11 illustrates the carriage by the actuator 39a of the by-passvalve unit 235. The latter may for example include the valve stoppersuch as ball 236 biased against seat ring 237 by the yieldable biasingmeans in the form of a compression spring 238. The latter is retainedwithin a plug 239 threaded into the actuator piston 240 and 241, and itacts on the ball 236 via a plunger 242 slidable within a bore 243 in theplug. Fluid by-passed by the ball escapes from closing chamber 244 tothe opening chamber 245, via ducts 246 and 247 in the actuator piston. Atelescoping hydraulic control connection to the by-pass valve may takethe form of a hollow pin 248 sealed at 248a and carried by the actuatorpiston 251 to slide up and down in the pin bore 249 formed in the body250, corresponding to housing 11 in FIG. 2. This arrangement provides ahydraulic connection from port 258 through .ports 300 and 301 andthrough which control fluid pressure enters the control fluid chamber249a to urge the piston 242 toward the ball 236. Actuator 251 alsocorresponds to actuator 39 in FIG. 2. Opening pressure is led viaporting 253 to the opening chamber 245.

FIG. 12 illustrates a modified modulator valve unit 260 incorporated ina body 261 which also carries a check valve 262 (corresponding to checkvalve 131 in FIG. 3) and an accumulator 263 (corresponding toaccumulator 128 in FIG. 3). The check valve unit 262 includes a ballcheck 264 spring urged at 265 against a seat ring 266,'and correspondsto check valve 131 of FIG. 3. When valve 264 opens, pressure is appliedto the four-way valve (not shown) which may have a position applyingpressure to port 272 to be described.

Pressure is communicated to the accumulator 263 via the porting 267 and268, such pressure also being communicated to the control piston 269acting via plunger 270 to bias the modulator valve ball 271 against seatring 271a. When the ball 271 is displaced upwardly off the seat, excessfluid pressure in port 272 (communicating with the closing chamber)escapes to side port 273 and to the openingchamber at the actuatorpiston in the manner as described in FIG. 3. A spring 274 assists inholding the ball 271 closed. Note insert legs 275 connected to the ring271a, and retained by insert sleeve 276 defining the bore 277 in whichthe piston 269 works. Thus, ring 271a is held by legs 275 in sealingposition.

Provision is also made for operation of a switch in a circuitcontrolling a suitable indicator, as at the surface in an off-shoreembodiment. The switch arm in this case consists of a rod 278 carried bythe piston 269 and projecting vertically for engagement with a terminalcontact 279 upon upward displacement of the piston by the ball 271, tocomplete the indicator circuit. Contact 279 is urged downwardly by aspring 280 adapted to yield upwardly as the ball 271 lifts the pistonand rod 278, insulation 281 and 282 confining the contact and springagainst electrical contact with the insert 283 in which these elementsare housed. The insert in turn fits within bore 284 within receptacle285 carried by the body 261. The spring has electrical circuitcommunication via terminal 286 with the indicator indicatedschematically at 287. I

The accumulator unit 263 may comprise a piston 290 slidable in bore 291to compress gas in chamber 292 in response to increased fluid pressuretransmission to chamber 293.

The apparatus of the invention may be used in either land or sub-seainstallations. Also, the apparatus works equally well whether the pipestring is being run into or out of a well. Further, after relief ofexcess pressure in the closing chamber associated with passing of thepipe joint through the packer, the modulating valve closes and theoriginal conditions of packer constriction about the pipe string arerestored.

What is claimed is:

1. ln a system that includes housing structure for passing a well stringvertically therethrough, a string engaging tool movable generallylaterally in the housing toward and away from the string, and a fluidpressure responsive actuator for the tool, there being first and secondchambers in the housing to receive fluid pressure acting to urge theactuator in opposite directions, the fluid in the first chamber beingsubject to excess pressure development in response to engagement of alongitudinally passing string enlargement with the tool tending todisplace the latter and the actuator, the combination comprising a.supply means to selectively supply actuating fluid pressure to saidchambers, and

b. modulator means in communication with the fluid pressure supply tothe first chamber and operable to relieve said excess pressuredevelopment therein in response to entry of said enlargement into thetool.

2. The combination of claim 1 wherein said tool comprises a packerannulus which is radially constrictable by the actuator, and which isexpansible radially in response to string joint passage forciblytherethrough.

3. In a system that includes housing structure for passing a well stringvertically therethrough, a string engaging tool movable generallylaterally in the housing toward and away from the string, and a fluidpressure responsive actuator for the tool, there being first and secondchambers in the housing to receive fluid pressure acting to urge theactuator in opposite directions, the fluid in the first chamber beingsubject to excess pressure development in response to engagement of alongitudinally passing string enlargement with the tool tending todisplace the latter and the actuator, the combination comprising a.supply means to selectively supply actuating fluid pressure to saidchambers, and

b. modulator means in communication with the fluid pressure supply tothe first chamber and operable to relieve said excess pressuredevelopment therein,

c. the modulator means being in operative communication with the secondchamber to effect a pressure increase therein in response to excesspressure development in the first chamber.

4. In a system that includes housing structure for passing a well stringvertically therethrough, a string engaging tool movable generallylaterally in the housing toward and away from the string, and a fluidpressure responsive actuator for the tool, there being first and secondchambers in the housing to receive fluid pressure acting to urge theactuator in opposite directions, the fluid in the first chamber beingsubject to excess pressure development in response to engagement of alongitudinally passing string enlargement with the tool tending todisplace the latter and the actuator, the combination comprising a.supply means to selectively supply actuating fluid pressure to saidchambers, and

b. modulator means in communication with the fluid pressure supply tothe first chamber and operable to relieve said excess pressuredevelopment therein,

c. said modulator means including a pressure relief valve communicatingwith the .fluid pressure supplied the first chamber.

5. In a system that includes housing structure for passing a well stringvertically therethrough, a string engaging tool movable generallylaterally in the housing toward and away from the string, and a fluidpressure responsive actuator for the tool, there being first and secondchambers in the housing to receive fluid pressure acting to urge theactuator in opposite directions, the fluid in the first chamber beingsubject to excess pressure development in response to engagement of alongitudinally passing string enlargement with the tool tending todisplace the latter and the actuator, the combination comprising a.supply means to selectively supply actuating fluid pressure to saidchambers,

b. modulator means in communication with the fluid pressure supply tothe first chamber and operable to relieve said excess pressuredevelopment therein, and

c. a passage communicating between said chambers, said modulator meanscontrolling fluid pressure communication from the first to the secondchambers for effecting said relief of excess pressure development in thefirst chamber.

6. The combination of claim 5 including a signaling circuit comprising aswitch operable in response to bypassing of fluid to the second chambervia the modulator means, and a signaling device electrically connectedin circuit with the switch.

7. The combination of claim 6 including said well string suspended by avessel to hang in the ocean and in a well below the ocean floor, saiddevice being on the vessel and said switch being at a stack of well headequipment at the ocean floor.

8. The combination of claim 6 wherein the switch includes a spring-urgedcontact adapted to be displaced to increase the spring tension inresponse to said fluid by-passing.

9. The combination of claim 5 wherein said modulator means includes aby-pass valve controlling said fluid pressure communication from thefirst to the second chambers.

10. The combination of claim 9 wherein said by-pass valve is outside thehousing.

11. The combination of claim 9 wherein said modulator means alsoincludes biasing means yieldably biasing the valve toward a positionblocking said fluid pressure communication from the first to the secondchambers.

12. The combination of claim 11 wherein said biasing means includescontrol fluid pressure from a source out of communication with saidchambers.

13. The combination of claim 11 wherein said biasing means comprisescontrol fluid pressure, and a piston responsive to said control fluidpressure to transmit biasing force to the valve.

14. The combination of claim 13 in which said biasing means alsoincludes a spring under tension, and means to adjust said tension.

15. The combination of claim 13 including piping communicating themodulator means and said first chamber with the accumulator and oflength such that an excess pressure wave from the first chamber isbypassed by said by-pass valve toward the second chamber prior totransmission of the wave via said piping to said accumulator.

16. The combination of claim 13 wherein said supply means includes acontrol valve having one position in which actuating fluid pressure issupplied to the first chamber but not to the second chamber, and asecond position in which actuating fluid pressure is supplied to thesecond chamber but not to the first chamber.

17. The combination of claim 16 in which said control valve in saidfirst position communicates the second chamber with an outlet and viapiping of such length that an actuating fluid pressure wave passed bythe by-pass valve is supplied to the second chamber prior totransmission to the outlet via the control valve.

18. The combination of claim 16 wherein said supply means includes asource of actuating fluid pressure and a pressure regulator connectedbetween said source and the control valve.

[9. The combination of 'claim 16 including an accumulator supplying saidcontrol fluid pressure.

20(The combination of claim l9including a support body containing saidaccumulator and said by-pass valve.

21. The combination of claim 20 including a check valve contained bysaid body and operable to transmit pressure from the accumulator to saidcontrol valve but blocking reverse transmission therebetween.

22. The combination of claim 9 wherein said by-pass valve in inside thehousing. 23. The combination of claim 22 wherein said bypass valve iscarried by the actuator.

24. The combination of claim 23 wherein the modulator means alsoincludes yieladable biasing means biasing the valve toward a positionblocking fluid pressure communication from the first to the secondchambers.

25. The combination of claim 23 including a telescopic connectionbetween the actuator and housing structure and defining porting throughwhich control fluid pressureis transmissible to a biasing piston actingto biasthe by-pass valve toward a position blocking said fluid pressurecommunication from the first to the second chambers.

26. For use in a system that includes housing structure for passing awell string vertically therethrough, a string engaging tool movablegenerally laterally in the housing toward and away from the string, anda fluid pressure responsive actuator for the tool, there being first andsecond chambers in the housing to receive fluid pressure acting to urgethe actuator in opposite directions, the pressure in the first chamberbeing subject to increase to excessive levels in response to engagementof a vertically passing string enlargement with the tool tendingtodisplace the latter and the actuator, the combination comprising a.supply means to selectively supply actuating fluid pressure to thechambers, and

b, modulator means operable, while actuating fluid pressure is beingsupplied tothe first chamber, to increase the fluid pressure in thesecond chamber and in response to displacement of the tool relativelyaway from the string so as to cause the actuator to move toward theinterior of the first chamber.

27. The combination of claim 26 wherein said modulator means is in fluidpressure by-passing communication with said chambers in response to saidtool displacement.

28. In the operation of a system that comprises annular packer meanswhich is radially forcibly constricted to engage a well string beingpassed longitudinally therethrough, and means including a packeractuator forming a first chamber receiving fluid pressure acting to urgethe actuator in a direction to effect said packer constriction, and asecond chamber subsequently to receive fluid pressure acting to urge theactuator in a direction relieving packer constriction to allow radialexpansion of the packer away from the string, the pressure in the firstchamber being subjected to increase to excessive level in response toengagement of an enlargement on the string with the constricted packerand tending to expand the packer, the steps that include a. continuingthe supply of actuating fluid pressure to the first chamber, and

b. suddenly increasing the fluid pressure in the second chamber inresponse to said engagement.

29. The method of claim 28 wherein said sudden increase of fluidpressure in the second chamber is effected by controllably by-passing tothe second chamber excess pressurized fluid from the first chamber.

30. The method of claim 29 wherein said by-passing is effected inresponse to detection of an increase of pressure in the first chamber tosaid excessive level.

31. For use in a sub-sea system that includes housing structure forpassing a well string longitudinally therethrough, a string engagingtool movable generally laterally in the housing toward and away from thestring, and a fluid pressure responsive actuator for the tool, therebeing first and second chambers in the housing to receive fluid pressureacting to urge the actuator in opposite directions, the pressure in thefirst chamber being subject to increase to excessive levels in responseto engagement of a longitudinally passing string enlargement with thetool tending to displace the latter and the actuator, the combinationcomprising modulator means operable, while actuating fluid pressure isbeing supplied to the first chamber, to increase the fluid pressure inthe second chamber and in response to increase of fluid pressure in thefirst chamber caused by force transmission from the enlargement to theactuator via the tool, said modulator means including a bypass valve,biasing means including an accumulator for biasing the valve toward aposition blocking actuating fluid pressure communication from the firstto the second chambers, a first pipe to communicate the inlet side ofthe by-pass valve with the first chamber, a second pipe to communicatethe outlet side of the bypass valve with the second chamber, and meansto controllably communicate fluid pressure to said accumulator to supplysaid control fluid pressure.

32. The combination of claim 31 wherein said last named means comprisesa valve operable to communicate fluid pressure from said first pipe tosaid accumulator when the pressure in said first chamber increases tosaid excessive level, and to communicate fluid pressure from said secondpipe to said accumulator in response to fluid pressure communication tosaid second chamber tending to hold said by-pass valve closed.

33. The combination of claim 31 wherein said last named means comprisesa surface control, and an elongated pipe communicating said control withsaid accumulator.

34. The combination of claim 31 including a pressure differential switchconnected across an orifice in said second pipe, said switch beingoperable to electrically control an indicator at the surface.

35. The combination of claim 31 including a fourway valve connected withsaid first and second pipes to selectively control actuating pressuresupply thereto, the four-way valve having an outlet to which anotherpipe is connected to pass fluid exhausted from one of the first andsecond chambers, and a pressure switch connected in said other pipe.

36. ln the operation of offshore drilling equipment wherein a pipestring extends longitudinally through a closed blow-out preventer at asub-sea location, the preventer containing a fluid pressure chamber, thestring including connectors of larger diameter than the pipe diameter,the steps that include a. effecting longitudinal displacement of thepipe,

b. detecting pressure change in said chamber resulting from the movementof a connector into engagement with the sub-sea closed preventer, and

c. adjusting the pipe string longitudinally to move the connector awayfrom the preventer.

37. The method of claim 36 wherein the equipment includes a drillingbarge from which the string is suspended to be subject to up and downdisplacement due to wave action, said adjustment step being carried outto an extent preventing subsequent engagement of the connector with theclosed preventer due to said up and down displacement.

1. In a system that includes housing structure for passing a well stringvertically therethrough, a string engaging tool movable generallylaterally in the housing toward and away from the string, and a fluidpressure responsive actuator for the tool, there being first and secondchambers in the housing to receive fluid pressure acting to urge theactuator in opposite directions, the fluid in the first chamber beingsubject to excess pressure development in response to engagement of alongitudinally passing string enlargement with the tool tending todisplace the latter and the actuator, the combination comprising a.supply means to selectively supply actuating fluid pressure to saidchambers, and b. modulator means in communication with the fluidpressure supply to the first chamber and operable to relieve said excesspressure development therein in response to entry of said enlargementinto the tool.
 2. The combination of claim 1 wherein said tool comprisesa packer annulus which is radially constrictable by the actuator, andwhich is expansible radially in response to string joint passageforcibly therethrough.
 3. In a system that includes housing structurefor passing a well string vertically therethrough, a string engagingtool movable generally laterally in the housing toward and away from thestring, and a fluid pressure responsive actuator for the tool, therebeing first and second chambers in the housing to receive fluid pressureacting to urge the actuator in opposite directions, the fluid in thefirst chamber being subject to excess pressure development in responseto engagement of a longitudinally passing string enlargement with thetool tending to displace the latter and the actuator, the combinationcomprising a. supply means to selectively supply actuating fluidpressure to said chambers, and b. modulator means in communication withthe fluid pressure supply to the first chamber and operable to relievesaid excess pressure development therein, c. the modulator means beingin operative communication with the second chamber to effect a pressureincrease therein in response to excess pressure development in the firstchamber.
 4. In a system that includes housing structure for passing awell string vertically therethrough, a string engaging tool movablegenerally laterally in the housing toward and away from the string, anda fluid pressure responsive actuator for the tool, there being first andsecond chambers in the housing to receive fluid pressure acting to urgethe actuator in opposite directions, the fluid in the first chamberbeing subject to excess pressure development in response to engagementof a longitudinally passing string enlargement with the tool tending todisplace the latter and the actuator, the combination comprising a.supply means to selectively supply actuating fluid pressure to saidchambers, and b. modulator means in communication with the fluidpressure supply to the first chamber and operable to relieve said excesspressure development therein, c. said modulator means including apressure relief valve communicating with the fluid pressure supplied thefirst chamber.
 5. In a system that includes housing structure forpassing a well string vertically therethrough, a string engaging toolmovable generally laterally in the housing toward and away from thestring, and a fluid pressure responsive actuator for the tool, therebeing first and second chambers in the housing to receive fluid pressureacting to urge the actuator in opposite directions, the fluid in thefirst chamber being subject to excess pressure development in responseto engagement of a longitudinally passing string enlargement with thetool tending to displace the latter and the actuator, the combinationcomprising a. supply means to selectively supply actuating fluidpressure to said chambers, b. modulator means in communication with thefluid pressure supply to the first chamber and operable to relieve saidexcess pressure development therein, and c. a passage communicatingbetween said chambers, said modulator means controlling fluid pressurecommunication from the first to the second chambers for effecting saidrelief of excess pressure development in the first chamber.
 6. Thecombination of claim 5 including a signaling circuit comprising a switchoperable in response to by-passing of fluid to the second chamber viathe modulator means, and a signaling device electrically connected incircuit with the switch.
 7. The combination of claim 6 including saidwell string suspended by a vessel to hang in the ocean and in a wellbelow the ocean floor, said device being on the vessel and said switchbeing at a stack of well head equipment at the ocean floor.
 8. Thecombination of claim 6 wherein the switch includes a spring-urgedcontact adapted to be displaced to increase the spring tension inresponse to said fluid by-passing.
 9. The combination of claim 5 whereinsaid modulator means includes a by-pass valve controlling said fluidpressure communication from the first to the second chambers.
 10. Thecombination of claim 9 Wherein said by-pass valve is outside thehousing.
 11. The combination of claim 9 wherein said modulator meansalso includes biasing means yieldably biasing the valve toward aposition blocking said fluid pressure communication from the first tothe second chambers.
 12. The combination of claim 11 wherein saidbiasing means includes control fluid pressure from a source out ofcommunication with said chambers.
 13. The combination of claim 11wherein said biasing means comprises control fluid pressure, and apiston responsive to said control fluid pressure to transmit biasingforce to the valve.
 14. The combination of claim 13 in which saidbiasing means also includes a spring under tension, and means to adjustsaid tension.
 15. The combination of claim 13 including pipingcommunicating the modulator means and said first chamber with theaccumulator and of length such that an excess pressure wave from thefirst chamber is by-passed by said by-pass valve toward the secondchamber prior to transmission of the wave via said piping to saidaccumulator.
 16. The combination of claim 13 wherein said supply meansincludes a control valve having one position in which actuating fluidpressure is supplied to the first chamber but not to the second chamber,and a second position in which actuating fluid pressure is supplied tothe second chamber but not to the first chamber.
 17. The combination ofclaim 16 in which said control valve in said first position communicatesthe second chamber with an outlet and via piping of such length that anactuating fluid pressure wave passed by the by-pass valve is supplied tothe second chamber prior to transmission to the outlet via the controlvalve.
 18. The combination of claim 16 wherein said supply meansincludes a source of actuating fluid pressure and a pressure regulatorconnected between said source and the control valve.
 19. The combinationof claim 16 including an accumulator supplying said control fluidpressure.
 20. The combination of claim 19 including a support bodycontaining said accumulator and said by-pass valve.
 21. The combinationof claim 20 including a check valve contained by said body and operableto transmit pressure from the accumulator to said control valve butblocking reverse transmission therebetween.
 22. The combination of claim9 wherein said by-pass valve in inside the housing.
 23. The combinationof claim 22 wherein said by-pass valve is carried by the actuator. 24.The combination of claim 23 wherein the modulator means also includesyieladable biasing means biasing the valve toward a position blockingfluid pressure communication from the first to the second chambers. 25.The combination of claim 23 including a telescopic connection betweenthe actuator and housing structure and defining porting through whichcontrol fluid pressure is transmissible to a biasing piston acting tobias the by-pass valve toward a position blocking said fluid pressurecommunication from the first to the second chambers.
 26. For use in asystem that includes housing structure for passing a well stringvertically therethrough, a string engaging tool movable generallylaterally in the housing toward and away from the string, and a fluidpressure responsive actuator for the tool, there being first and secondchambers in the housing to receive fluid pressure acting to urge theactuator in opposite directions, the pressure in the first chamber beingsubject to increase to excessive levels in response to engagement of avertically passing string enlargement with the tool tending to displacethe latter and the actuator, the combination comprising a. supply meansto selectively supply actuating fluid pressure to the chambers, and b.modulator means operable, while actuating fluid pressure is beingsupplied to the first chamber, to increase the fluid pressure in thesecond chamber and in response to displacement of the tool relativelyaway from the string so as to cause the actuator to move toward Theinterior of the first chamber.
 27. The combination of claim 26 whereinsaid modulator means is in fluid pressure by-passing communication withsaid chambers in response to said tool displacement.
 28. In theoperation of a system that comprises annular packer means which isradially forcibly constricted to engage a well string being passedlongitudinally therethrough, and means including a packer actuatorforming a first chamber receiving fluid pressure acting to urge theactuator in a direction to effect said packer constriction, and a secondchamber subsequently to receive fluid pressure acting to urge theactuator in a direction relieving packer constriction to allow radialexpansion of the packer away from the string, the pressure in the firstchamber being subjected to increase to excessive level in response toengagement of an enlargement on the string with the constricted packerand tending to expand the packer, the steps that include a. continuingthe supply of actuating fluid pressure to the first chamber, and b.suddenly increasing the fluid pressure in the second chamber in responseto said engagement.
 29. The method of claim 28 wherein said suddenincrease of fluid pressure in the second chamber is effected bycontrollably by-passing to the second chamber excess pressurized fluidfrom the first chamber.
 30. The method of claim 29 wherein saidby-passing is effected in response to detection of an increase ofpressure in the first chamber to said excessive level.
 31. For use in asub-sea system that includes housing structure for passing a well stringlongitudinally therethrough, a string engaging tool movable generallylaterally in the housing toward and away from the string, and a fluidpressure responsive actuator for the tool, there being first and secondchambers in the housing to receive fluid pressure acting to urge theactuator in opposite directions, the pressure in the first chamber beingsubject to increase to excessive levels in response to engagement of alongitudinally passing string enlargement with the tool tending todisplace the latter and the actuator, the combination comprisingmodulator means operable, while actuating fluid pressure is beingsupplied to the first chamber, to increase the fluid pressure in thesecond chamber and in response to increase of fluid pressure in thefirst chamber caused by force transmission from the enlargement to theactuator via the tool, said modulator means including a by-pass valve,biasing means including an accumulator for biasing the valve toward aposition blocking actuating fluid pressure communication from the firstto the second chambers, a first pipe to communicate the inlet side ofthe by-pass valve with the first chamber, a second pipe to communicatethe outlet side of the by-pass valve with the second chamber, and meansto controllably communicate fluid pressure to said accumulator to supplysaid control fluid pressure.
 32. The combination of claim 31 whereinsaid last named means comprises a valve operable to communicate fluidpressure from said first pipe to said accumulator when the pressure insaid first chamber increases to said excessive level, and to communicatefluid pressure from said second pipe to said accumulator in response tofluid pressure communication to said second chamber tending to hold saidby-pass valve closed.
 33. The combination of claim 31 wherein said lastnamed means comprises a surface control, and an elongated pipecommunicating said control with said accumulator.
 34. The combination ofclaim 31 including a pressure differential switch connected across anorifice in said second pipe, said switch being operable to electricallycontrol an indicator at the surface.
 35. The combination of claim 31including a four-way valve connected with said first and second pipes toselectively control actuating pressure supply thereto, the four-wayvalve having an outlet to which another pipe is connected to pass fluidexhausted from one of the first and seCond chambers, and a pressureswitch connected in said other pipe.
 36. In the operation of offshoredrilling equipment wherein a pipe string extends longitudinally througha closed blow-out preventer at a sub-sea location, the preventercontaining a fluid pressure chamber, the string including connectors oflarger diameter than the pipe diameter, the steps that include a.effecting longitudinal displacement of the pipe, b. detecting pressurechange in said chamber resulting from the movement of a connector intoengagement with the sub-sea closed preventer, and c. adjusting the pipestring longitudinally to move the connector away from the preventer. 37.The method of claim 36 wherein the equipment includes a drilling bargefrom which the string is suspended to be subject to up and downdisplacement due to wave action, said adjustment step being carried outto an extent preventing subsequent engagement of the connector with theclosed preventer due to said up and down displacement.